Organic luminescence device

ABSTRACT

An organic luminescence device is constituted by a pair of an anode and a cathode, and at least one organic layer disposed between the anode and the cathode. The above-mentioned at least one organic layer includes a layer of a fused polynuclear compound represented by the following formula (I):  
                 
 
     In the above formula (I), X 1 , X 2  and X 3  may preferably oxygen atom or C(CN) 2 . The device using the fused polynuclear compound of the formula (I) exhibits a high-luminance luminescence characteristic for a long period of time.

FIELD OF THE INVENTION AND RELATED ART

[0001] The present invention relates to an organic luminescence deviceusing a specific fused polynuclear (or polycyclic) compound,particularly an organic luminescence device wherein an electric field isapplied to a film of an organic compound comprising the fusedpolynuclear compound to cause luminescence.

[0002] An organic luminescence device is a device such that a thin filmcontaining a fluorescent organic compound is sandwiched between an anodeand a cathode, and holes and electrons are injected from the anode andthe cathode, respectively, into the fluorescent organic compound layerto generate excitons which emit light at the time of being returned to aground state.

[0003] For example, according to Eastman Kodak's study (“Appl. Phys.Lett.”, 51,913 (1987)), when a voltage of ca. 10 volts is applied to afunction separation-type organic luminescence device including twolayers of an aluminum quinolinol complex (as electron transport andluminescence material) and a triphenylamine derivative (as holetransport material) disposed between an anode of ITO (indium tin oxide)and a cathode of a magnesium-silver alloy, an emission luminance of ca.1000 cd/m² is obtained. Related patents thereof are, e.g., U.S. Pat.Nos. 4,539,507; 4,720,432; and 4,885,211.

[0004] Further, it is possible to effect luminescence ranging fromultraviolet region to infrared region by appropriately changing thespecies of a fluorescent organic compound used. In recent years, studieson various fluorescent organic compounds have been made extensively as,e.g., described in U.S. Pat. Nos. 5,151,629; 5,409,783; and 5,382,477;and Japanese Laid-Open Patent Application (JP-A) Nos. 2-247278 (corr. toU.S. Pat. Nos. 5,130,603 and 6,093,864); 3-255190 (corr. to U.S. Pat.No. 5,227,252); 5-202356: 9-202878; and9-227576.

[0005] In addition to the above-mentioned organic luminescence devicesusing low-molecular weight materials, an organic luminescence deviceusing a conjugated system polymer has been reported by a research groupof Cambridge University (“Nature”, 347,539 (1990)). According to thisreport, by forming a single layer of PPV (polyphenylenevinylene) bymeans of wet coating, luminescence from the layer has been confirmed.

[0006] Related patents as to organic luminescence devices usingconjugated system polymers may include: U.S. Pat. Nos. 5,247,190;5,514,878; and 5,672,678; JP-A 4-145192 (corr. to U.S. Pat. Nos.5,317,169 and 5,726,457) and JP-A 5-247460.

[0007] As described above, recent progress of the organic luminescencedevices is noticeable. More specifically, it is possible to realize athin and light-weight luminescence device allowing high luminance at lowapplied voltage, variety of emission wavelength and high-speedresponsiveness, thus suggesting possibilities of application to varioususes.

[0008] However, the organic luminescence devices are required to exhibitfurther improved performances such as light output at high luminance andhigh conversion efficiency. Further, the organic luminescence deviceshave been accompanied with problems in terms of durability such as achange in luminance with time due to continuous use for a long time, anda deterioration (e.g., an occurrence of dark spots due to leakage ofcurrent) by ambient gas containing oxygen or by humidity.

[0009] As fluorescent organic compounds for use in an electron injectionlayer and/or an electron transport layer, a large number of heterocycliccompounds have been proposed as described in, e.g., JP-A 6-184125,9-286980 and 9-291274. However, resultant emission luminances anddurabilities and luminescence efficiencies have been still insufficient.

SUMMARY OF THE INVENTION

[0010] A principal object of the present invention is to provide anorganic luminescence device having solved the above-mentioned problems.

[0011] A specific object of the present invention is to provide anorganic luminescence device capable of effecting output of light withvery high efficiency and luminance by using a specific fused polynucleararomatic compound.

[0012] Another object of the present invention is to provide an organicluminescence device having a high durability.

[0013] A further object of the present invention is to provide anorganic luminescence device which can be prepared readily and relativelyinexpensively.

[0014] According to the present invention, there is provided an organicluminescence device, comprising:

[0015] a pair of an anode and a cathode, and

[0016] at least one organic layer disposed between the anode and thecathode, wherein

[0017] at least one organic layer described above comprises a layercomprising at least one species of a fused polynuclear compoundrepresented by the following formula (I):

[0018] wherein R₁ to R₁₂ independently denote a hydrogen atom, an alkylgroup, a substituted or unsubstituted aralkyl group, a substituted orunsubstituted aryl group, a substituted or unsubstituted heterocyclicgroup, a substituted amino group, a cyano group or a halogen atom; R₁ toR₄, R₅ to R₈ and R₉ to R₁₂ being independently capable of includingadjacent two groups forming a substituted or unsubstituted aliphaticcyclic structure, a substituted or un-substituted aromatic ringstructure, or a substituted or unsubstituted heterocyclic structure, andX₁, X₂ and X₃ independently denote an oxygen atom, a sulfur atom,C(CN)₂, C(CF₃)₂, C(Ar₁)Ar₂ or N—Ar₃, wherein Ar₁, Ar₂ and Ar₃independently denote a substituted or unsubstituted aryl group or asubstituted or unsubstituted heterocyclic group; Ar₁ and Ar₂ beingcapable of forming a ring structure.

[0019] In the above formula (I), at least one of X₁, X₂ and X₃ maypreferably be C(CN)₂. Particularly, X₁, X₂ and X₃ may desirably beC(CN)₂ at the same time as shown by the following formula (II):

[0020] In another preferred embodiment, X₁, X₂ and X₃ may desirably be O(oxygen atom) at the same time as shown by the following formula (III):

[0021] Further, in the present invention, the above-mentioned layer offused polynuclear compound of the formula (I), preferably formula (II)or (III), may desirably be any one of an electron injection layer, anelectron transport layer and a hole blocking layer.

[0022] These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIGS. 1 to 6 are respectively a schematic sectional view showingan embodiment of the organic luminescence device according to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinbelow, the present invention will be described morespecifically.

[0025] The organic luminescence device according to the presentinvention comprises a pair of electrodes composed of an anode and acathode and at least one organic layer disposed between the pair ofelectrodes. Examples of such an organic layer may include a luminescencelayer, a hole transport layer, an electron transport layer, an electroninjection layer and a hole blocking layer.

[0026] In the present invention, the above-mentioned at least oneorganic layer may preferably have one to six layer structuresspecifically described hereinafter with reference to FIGS. 1-6.

[0027] In the present invention, at least one organic layer describedabove may preferably include at least one layer comprising a fusedpolynuclear compound represented by any one of the above-mentionedformulas (I) to (III).

[0028] Specific examples of R₁ to R₁₂ and Ar₁ to Ar₃ in the formulas (I)to (III) for the fused polynuclear compound used in the presentinvention will be shown below.

[0029] Examples of alkyl group may include methyl, ethyl, n-propyl,iso-propyl, n-butyl, tert-butyl and octyl.

[0030] Examples of aralkyl group may include benzyl and phenethyl.

[0031] Examples of aryl group may include phenyl, biphenyl, terphenyl,naphthyl, anthryl, phenanthryl, pyrenyl, tetracenyl, pentacenyl andfluorenyl.

[0032] Examples of heterocyclic group may include thienyl, pyrrolyl,pyridyl, quinolyl, carbazolyl, oxazolyl, oxadiazolyl, thiazolyl,thiadiazolyl, terthienyl and terpyrrolyl.

[0033] Examples of substituted amino group may include dimethylamino,diethylamino, dibenzylamino, diphenylamino, ditolylamino anddianisolylamino.

[0034] Examples of aliphatic cyclic structure may include cyclopropanering and cyclohexane ring.

[0035] Examples of aromatic ring structure and heterocycle structure mayinclude rings comprising those for aryl group and heterocyclic group,respectively.

[0036] Examples of substituents for the above-mentioned groups (orstructures) for R₁ to R₁₂ and Ar₁ to Ar₃ may include: alkyl groups suchas methyl, ethyl and propyl; aralkyl groups such as benzyl andphenethyl; aryl groups such as phenyl, naphthyl, anthryl, phenanthryl,pyrenyl, tetracenyl, pentacenyl, and fluorenyl; heterocyclic groups suchas thienyl, pyrrolyl and pyridyl; amino groups such as dimethylamino,diethylamino, dibenzylamino, diphenylamino, ditolylamino anddianisolylamino; alkoxy groups such as methoxy, ethoxy, propoxy andphenoxy; cyano group; and nitro group.

[0037] Hereinafter, the fused polynuclear compounds of the formulas (I)to (III) used in the present invention will be shown below specificallyby their structural formulas (Example Compound Nos. 1 to 35) for therespective formulas (I) to (III) but are not restricted to the followingspecific compounds.

[0038] As apparent from the above fused polynuclear compounds offormulas (I), (II) and (III) (Ex. Comp. Nos. 1 to 35), the fusedpolynuclear compound used in the present invention may include truxenone(tribenzo[a,f,k]triindenone) (Ex. Comp. No. 1) and its derivatives.

[0039] More specifically, such derivatives of truxenone may include: acompound (Ex. Comp. No. 2) having three carbonyl portions (>C=0) andsubstituted aryl groups; a compound (Ex. Comp. No. 9) having asubstituted one carbonyl portion where oxygen atom is replaced by dicyanmethyl group (C(CN)₂) (dicyan methylation); a compound (Ex. Comp. No.11) having substituted three carbonyl portions where each oxygen atom isreplaced by sulfur atom; a compound (Ex. Comp. No. 18) havingsubstituted three carbonyl portions where each oxygen atom is replacedby C(CF₃)₂; a compound (Ex. Comp. No. 19) having substituted threecarbonyl portions where each oxygen atom is substituted by C(Ar₁)Ar₂(Ar₁═Ar₂═

[0040] and a compound (Ex. Comp. No. 22) having one dicyan methyl groupand substituted two carbonyl portions where each oxygen atom is replacedby N—Ar₃ (Ar₃═

[0041] Truxenone (Ex. Comp. No. 1) is a compound having a centralbenzene ring (six-membered ring) connected to three five-membered ringsat three different positions and further connected to three benzenerings via each five-membered ring.

[0042] The fused polynuclear compound used in the present invention maypreferably have a chemical structure comprising a central benzene ring,three five-membered rings connected to the central benzene ring, andthree six-membered rings each different from benzene ring and connectedto the three five-membered rings, respectively, as shown by Ex. Comp.Nos. 1 to 35.

[0043] Further, three five-membered rings each having the carbonylportion (>C=0) or carbonyl-corresponding portion (>C=) may include oneor two rings different from the remaining ring(s) in thecarbonyl(-corresponding) portion as in Ex. Comp. Nos. 9 and 22.

[0044] The fused polynuclear compound of formulas (I) to (III) used inthe present invention may be synthesized through known processesincluding those as described in, e.g., “Angew. Chem. Int. Ed. Engl.”,31, 1101 (1992), “Tetrahedron Lett.”, 38, 1081 (1997) and “TetrahedronLett.”, 40, 8625 (1999).

[0045] The first and second articles describe processes of synthesizingtoluxenone and the third article describes a process for effectingdicyan methylation of carbonyl portions (>C=0).

[0046] The fused polynuclear compound of the formulas (I) to (III) usedin the present invention is an excellent organic luminescence functionmaterial in terms of at least one of electron injection performance,electron transfer performance, hole blocking performance and durability,compared with conventional compounds, thus being a material suitable foran organic layer, particularly an electron injection layer, an electrontransport layer and/or a hole blocking layer. Further when such anorganic layer is formed by vacuum (vapor) deposition or wet coatingusing an appropriate solvent, the resultant organic layer is less liableto cause crystallization, thus being excellent in stability with time.

[0047] In the present invention, as described above, the organic layerdisposed between the pair of electrodes (anode and cathode) may beformed in one or a plurality of organic compound layers including atleast one layer thereof comprising the above-mentioned fused polynuclearcompound of the formulas (I) to (III). Further, such at least one layermay preferably function as an electron injection layer, an electrontransport layer or a hole blocking layer.

[0048] Each of the organic (compound) layers may preferably be formed ina thickness of at most 10 μm, more preferably at most 0.5 μm, mostpreferably 0.01-0.5 μm.

[0049] Hereinbelow, layer structures of the organic luminescence deviceaccording to the present invention will be described specifically withreference to FIGS. 1 to 6 each illustrating a preferred embodimentthereof.

[0050] Referring to FIGS. 1-6 the respective organic luminescencedevices basically include a substrate 1, an anode 2 disposed on thesubstrate 1, one or more organic layer disposed on the anode 2, and acathode 4 disposed on the one or more organic layer.

[0051] In an embodiment shown in FIG. 1, the organic layer is composedof a single layer exhibiting multifunctional performances in terms of ahole transport ability, an electron transportability and a luminescenceperformance. These performances may be given by using a singlemultifunctional compound or by mixing the respective functionalmaterials in a single layer.

[0052] In another embodiment shown in FIG. 2, the organic layer iscomposed of a hole transport layer 5 disposed on the anode 2 and anelectron transport layer 6 disposed on the hole transport layer 5. Inthis embodiment, a luminescent material also exhibits either one or bothof a hole transport performance and an electron transport performanceand is used in combination with a hole transport material free from aluminescence performance or an electron transport material free from aluminescence performance. In this embodiment, either one of the holetransport layer 5 and the electron transport layer 6 also functions asin the luminescence layer.

[0053] In another embodiment shown in FIG. 3, the organic layer iscomposed of three layers consisting of a hole transport layer 5, aluminescence layer 3 and an electron transport layer 6 disposed in thisorder on the anode 2. In this embodiment, carrier (hole/electron)transport performances and luminescence performance are functionallyseparated into the three layers which may appropriately be formed byusing functional materials exhibiting a hole transport performance, anelectron transport performance and a luminescence performance,respectively. As a result, it is possible to allow not only an increasedlatitude in selection of materials but also use of various compoundsdifferent in emission wavelength, thus resulting in a variety ofemission hues. Further, it also becomes possible to effectivelyconfining respective carriers or excitons in the luminescence layer 3,thus improving a luminescence efficiency.

[0054]FIG. 4 shows another embodiment of the organic luminescence deviceof the present invention. Referring to FIG. 4, the organic luminescencedevice has four layers as the organic layers including three functionallayers similar to those (hole transport layer 5, luminescence layer 3and electron transport layer 6) shown in FIG. 3 and further an electroninjection layer 7 disposed between the cathode 4 and the electrontransport layer 6. The use of the electron injection layer 7 iseffective in improving adhesive properties between the cathode 4 and theelectron transport layer 6 or electron injection performance, thusresulting in luminescence at a low applied voltage.

[0055]FIGS. 5 and 6 show other embodiments similar to those shown inFIGS. 3 and 4, respectively, except that a hole (or exciton) blockinglayer 8 for blocking passing of holes or excitons to the cathode side isdisposed between the electron transport layer 6 and the luminescencelayer 3. In these embodiments, by using a compound exhibiting a veryhigh ionization potential in the hole blocking layer 8, a resultantluminescence efficiency is effectively improved.

[0056] In the above-mentioned layer structures of organic luminescencedevice of the present invention, between the cathode 4 and theluminescence layer 3, the electron transport layer 6 or the electroninjection layer 7 may generally be disposed in contact with the cathode4, and the electron transport layer 6 or the hole blocking layer 8 maygenerally be disposed in contact with the luminescence layer 3. Further,the electron injection layer 7 and the hole blocking layer 8 maygenerally have a thickness smaller than the electron transport layer 6.

[0057] The layer structure of organic luminescence device of the presentinvention using the above-mentioned fused polynuclear compound is notrestricted to those described above with reference to FIGS. 1-6illustrating basic device structures of the organic luminescence deviceof the present invention.

[0058] The fused polynuclear compound used in the present invention(represented by any one of the formulas (I) to (III)) may preferably beused as a material suitable for the electron injection layer, theelectron transport layer and/or the luminescence layer but mayappropriately be used, as desired, in combination with conventionallyknown materials, such as hole transport compounds, luminescent compoundsand/or electron transport compounds shown below.

[0059] Hole Transport Material

[0060] Hole Transport Material

[0061] Electron Transport Luminescence Material

[0062] Luminescence Material

[0063] Luminescence Layer Matrix (Host) Material and Electron TransportMaterial

[0064] Polymer-Type Hole Transport Material

[0065] Polymer-Type Luminescence Material and Charge Transport Material

[0066] In the organic luminescence device according to the presentinvention, a layer of the fused polynuclear compound represented by theformulas (I) to (III) and other layers comprising organic compounds maygenerally be formed in a thin film by vacuum deposition or wet coatingusing an appropriate solvent for dissolving such organic compounds(including the fused polynuclear compound). Particularly, in the case ofusing the wet coating, it is also possible to form a film in combinationwith an appropriate binder resin.

[0067] The binder resin may appropriately be selected from various knownresins. Examples of the binder resin may include: polyvinyl carbazole,polycarbonate resin, polyester resin, polyarylate resin, polystyreneresin, acrylic resin, methacrylic resin, butyral resin, polyvinyl acetalresin, diallyl phthalate resin, phenolic resin, epoxy resin, siliconeresin, polysulfone resin and urea resin. These resins may be used singly(as a homopolymer) or in combination of two or more species (as acopolymer).

[0068] The binder resin may preferably be used in an amount of 0.01-20wt. parts, more preferably 0.1-10 wt. parts, per 1 wt. part of the fusedpolynuclear compound.

[0069] The anode (electrode) constituting the organic luminescencedevice of the present invention may desirably be formed of a materialhaving a work function as large as possible. Examples of such a materialmay include: metals such as gold, platinum, nickel, palladium, cobalt,selenium and vanadium; alloys of those metals; and metal oxides such astin oxide, zinc oxide, indium tin oxide (ITO) and indium zinc oxide.Further, it is also possible to use electroconductive polymers such aspolyaniline, polypyrrole, polythiophene, and polyphenylene sulfide.These materials may be used singly or in mixture.

[0070] On the other hand, the cathode (electrode) may desirably beformed of a material having a work function as small as possible.Examples of such a material may include: metals such as lithium, sodium,potassium, calcium, magnesium, aluminum, indium, silver, lead, tin andchromium; and alloys of these metals. It is also possible to use metaloxides such as ITO. The cathode may be formed in a single layer orplural layers.

[0071] The substrate for the organic luminescence device of the presentinvention is not particularly limited. Examples of the substrate mayinclude an opaque substrate such as a metal substrate or ceramicsubstrate, and a transparent substrate such as glass substrate, quartzsubstrate or plastic sheet. Further, it is also possible to controlemitted light by using a color filter film, a fluorescent colorconversion film or a dielectric reflection film, in combination with thesubstrate.

[0072] The organic luminescence device of the present invention mayfurther comprise a protective layer or a sealing layer in order toprevent contact of the organic luminescence device with ambient oxygenor moisture.

[0073] Examples of the protective layer may include: a diamond film, afilm of inorganic material such as metal oxide or metal nitride, a filmof polymer such as fluorine-containing resin, polyparaxylene,polyethylene, silicone resin or polystyrene, and a film of aphoto-curable resin. Further, it is possible to effect packaging of theorganic luminescence device per se by covering, e.g., glass substrate,gas-impermeable film or metal film with an appropriate sealing resin.

[0074] Hereinbelow, the present invention will be described morespecifically based on Examples but is not restricted to the Examples.

EXAMPLE 1

[0075] An organic luminescence device shown in FIG. 4 was prepared inthe following manner.

[0076] On a 0.7 mm-thick glass substrate 1, a 120 nm-thick ITO (indiumtin oxide) film (anode 2) was formed by sputtering to prepare atransparent electroconductive support, which was then successivelysubjected to ultrasonic cleaning with acetone and that with isopropylalcohol (IPA). The resultant transparent electroconductive support wasthen subjected to boiling cleaning with IPA and was dried, followed byUV/ozone cleaning.

[0077] On the thus-treated transparent electroconductive support, asolution of a hole transport material shown below in chloroform wasapplied by spin coating to form a 20 nm-thick hole transport layer 5.

[0078] On the hole transport layer 5, a 20 nm-thick luminescence layer 3of rubrene shown below and Alq3 (aluminum tris-quinolinol) shown below(1:20 by weight) was formed by co-vacuum deposition.

[0079] On the luminescence layer 3, a 40 nm-thick electron transportlayer 6 of Alq3 was formed by vacuum deposition.

[0080] On the electron transport layer 6, a 10 nm-thick electroninjection layer 7 of a fused polynuclear compound (Ex. Comp. No. 1) wasformed by vacuum deposition under conditions including a vacuum degree(pressure) of 1.0×10⁻⁴ Pa and a deposition rate of 0.2-0.3 nm/sec.

[0081] Then, on the electron injection layer 7, a 150 nm-thick metalelectrode (cathode 4) of an aluminum-lithium alloy (Li content: 1 atomic%) was formed by vacuum deposition (1.0×10⁻⁴ Pa; 1.0-1.2 nm/sec).

[0082] To the thus-prepared organic luminescence device as shown in FIG.4, a DC voltage of 4 volts was applied between the ITO electrode (anode2, positive pole) and the Al-Li electrode (cathode 4, negative pole),whereby a current was passed through the organic luminescence device ata current density of 4.5 mA/cm² and yellow luminescence was observed ata luminance of 880 cd/m².

[0083] Then, when the organic luminescence device was supplied with avoltage for 100 hours while keeping a current density of 4.0 mA/cm² in anitrogen atmosphere, a luminance of 810 cd/m² (as initial luminance) wasmerely decreased to 790 cd/m² even after 100 hours of the voltageapplication, thus exhibiting a good durability (less deterioration inluminance). The results are also shown in Table 1 appearing hereinafter.

EXAMPLES 2-15

[0084] Organic luminescence devices were prepared and evaluated in thesame manner as in Example 1 except that the fused polynuclear compound(Ex. Comp. No. 1) was changed to those (Ex. Comp. Nos. 4, 8, 10, 13, 16,18, 20, 23, 24, 26, 28, 32, 34 and 35), respectively.

[0085] The results are shown in Table 1.

COMPARATIVE EXAMPLE 1

[0086] An organic luminescence device was prepared and evaluated in thesame manner as in Example 1 except that the electron injection layer 7was not formed.

[0087] The results are shown in Table 2.

COMPARATIVE EXAMPLES 2-4

[0088] Organic luminescence devices were prepared and evaluated in thesame manner as in Example 1 except that the fused polynuclear compound(Ex. Comp. No. 1) was changed to the following comparative compoundsNos. 1-3, respectively.

[0089] The results are shown in Table 2.

[0090] Comparative Compound No. 1

[0091] Comparative Compound No. 2

[0092] Comparative Compound No. 3

TABLE 1 Initial Luminance Ex. Applied (at 4.0 mA/cm²) Ex. Comp. voltageLuminance Initial After 100 hr No. No. (V) (cd/m²) (cd/m²) (cd/m²) 1 1 4880 810 790 2 4 4 840 780 750 3 8 4 870 800 740 4 10 4 920 870 860 5 134 1050 990 960 6 16 4 1000 980 940 7 18 4 810 760 750 8 20 4 790 730 6909 23 4 850 820 800 10 24 4 860 800 750 11 26 4 770 730 690 12 28 4 810770 730 13 32 4 990 950 940 14 34 4 1020 950 930 15 35 4 960 920 890

[0093] TABLE 2 Comp. Initial Luminance Comp. Ex. Applied (at 4.0 mA/cm²)Ex. Comp. voltage Luminance Initial After 100 hr No. No. (V) (cd/m²)(cd/m²) (cd/m²) 1 None 4 630 590 410 2 Comp.1 4 260 240 No luminescence3 Comp.2 4 490 480 40 4 Comp.3 4 190 180 No luminescence

EXAMPLE 16

[0094] An organic luminescence device shown in FIG. 3 was prepared inthe following manner.

[0095] In a similar manner as in Example 1, a transparentelectroconductive support was prepared.

[0096] On the transparent electroconductive support, a 40 nm-thick holetransport layer 5 of a compound shown below was formed by vacuumdeposition.

[0097] On the hole transport layer 5, a 20 nm-thick luminescence layer 3of a compound shown below was formed by vacuum deposition.

[0098] On the luminescence layer 3, a 40 nm-thick electron transportlayer 6 of a fused polynuclear compound (Ex. Comp. No. 2) was formed byvacuum deposition (1.0×10⁻⁴ Pa;0.2-0.3 nm/sec).

[0099] Then, on the electron transport layer 6, a 150 nm-thick metalelectrode (cathode 4) of an aluminum-lithium alloy (Li content: 1 atomic%) was formed by vacuum deposition (1.0×10⁻⁴ Pa;1.0-1.2 nm/sec).

[0100] To the thus-prepared organic luminescence device as shown in FIG.3, a DC voltage of 8 volts was applied between the ITO electrode (anode2, positive pole) and the Al-Li electrode (cathode 4, negative pole),whereby a current was passed through the organic luminescence device ata current density of 7.6 mA/cm² and blue luminescence was observed at aluminance of 3800 cd/m².

[0101] Then, when the organic luminescence device was supplied with avoltage for 100 hours while keeping a current density of 7.0 mA/cm² in anitrogen atmosphere, a luminance of 3650 cd/m² (as initial luminance)was merely decreased to 3500 cd/m² even after 100 hours of the voltageapplication, thus exhibiting a good durability. The results are shown inTable 3 appearing hereinafter.

EXAMPLES 17-30

[0102] Organic luminescence devices were prepared and evaluated in thesame manner as in Example 16 except that the fused polynuclear compound(Ex. Comp. No. 2) was changed to those (Ex. Comp. Nos. 6, 9, 12, 15, 17,19, 21, 22, 25, 27, 29, 30, 31 and 33), respectively.

[0103] The results are shown in Table 3.

COMPARATIVE EXAMPLES 5-7

[0104] Organic luminescence devices were prepared and evaluated in thesame manner as in Example 16 except that the fused polynuclear compound(Ex. Comp. No. 2) was changed to the above-mentioned comparativecompounds Nos. 1-3, respectively.

[0105] The results are shown in Table 4. TABLE 2 Initial Luminance Ex.Applied (at 7.0 mA/cm²) Ex. Comp. voltage Luminance Initial After 100 hrNo. No. (V) (cd/m²) (cd/m²) (cd/m²) 16 2 8 3800 3650 3500 17 6 8 31503100 2950 18 9 8 3200 3100 2900 19 12 8 4600 4300 4150 20 15 8 4850 44504100 21 17 8 4450 4400 4100 22 19 8 2900 2700 2450 23 21 8 3350 32003000 24 22 8 2800 2500 2300 25 25 8 3050 2800 2550 26 27 8 3850 35003350 27 29 8 3700 3500 3350 28 30 8 4300 4000 3850 29 31 8 4000 38003600 30 33 8 3550 3400 3300

[0106] TABLE 4 Comp. Initial Luminance Comp. Ex. Applied (at 7.0 mA/cm²)Ex. Comp. voltage Luminance Initial After 100 hr No. No. (V) (cd/m²)(cd/m²) (cd/m²) 5 Comp.1 8 350 310 No luminescence 6 Comp.2 8 730 670 907 Comp.3 8 230 220 No luminescence

Example 31

[0107] An organic luminescence device shown in FIG. 5 was prepared inthe following manner.

[0108] On a transparent electroconductive support prepared in the samemanner as in Example 1, a 20 nm-thick hole transport layer 5 and a 20nm-thick luminescence layer 3 were formed in the same manner as inExample 1.

[0109] On the luminescence layer 3, a 10 nm-thick hole blocking layer 8of a fused polynuclear compound (Ex. Comp. No. 3) was formed by vacuumdeposition.

[0110] On the hole blocking layer 8, a 40 nm-thick electron transportlayer 6 of Alq3 was formed by vacuum deposition (1.0×10⁻⁴ Pa;0.2-0.3nm/sec).

[0111] Then, on the electron transport layer 6, a 150 nm-thick metalelectrode (cathode 4) of an aluminum-lithium alloy (Li content: 1 atomic%) was formed by vacuum deposition (1.0×10⁻⁴ Pa;1.0-1.2 nm/sec).

[0112] To the thus-prepared organic luminescence device as shown in FIG.5, a DC voltage of 8 volts was applied between the ITO electrode (anode2, positive pole) and the Al-Li electrode (cathode 4, negative pole),whereby a current was passed through the organic luminescence device ata current density 2 of 7.1 mA/cm and yellow luminescence was observed ata luminance of 7500 cd/m².

[0113] Then, when the organic luminescence device was supplied with avoltage for 100 hours while keeping a current density of 7.0 mA/cm in anitrogen atmosphere, a luminance of 7300 cd/m² (as initial luminance)was merely decreased to 6950 cd/m² even after 100 hours of the voltageapplication, thus exhibiting a good durability. The results are shown inTable 5 appearing hereinafter.

EXAMPLES 32-35

[0114] Organic luminescence devices were prepared and evaluated in thesame manner as in Example 31 except that the fused polynuclear compound(Ex. Comp. No. 3) was changed to compounds (Ex. Comp. Nos. 5, 7, 11 and14), respectively.

[0115] The results are shown in Table 5.

COMPARATIVE EXAMPLES 8-10

[0116] Organic luminescence devices were prepared and evaluated in thesame manner as in Example 31 except that the fused polynuclear compound(Ex. Comp. No. 3) was changed to the above-mentioned comparativecompounds Nos. 1-3, respectively.

[0117] The results are shown in Table 5. TABLE 5 Initial Luminance Ex.Applied (at 7.0 mA/cm²) Ex. Comp. voltage Luminance Initial After 100 hrNo. No. (V) (cd/m²) (cd/m²) (cd/m²) 31 3 8 7500 7300 6950 32 5 8 93509000 8600 33 7 8 8100 7950 7300 34 11 8 6800 6600 6200 35 14 8 7050 69006450 Comp Comp 8 1350 1300 190 Ex.8 No.1 Comp Comp 8 2600 2450 600 Ex.9No.2 Comp Comp 8 950 900 50 Ex.10 No.3

[0118] As described hereinabove, according to the present invention, byusing a fused polynuclear compound of the formula (I) (preferably theformula (II) or (III)) as a material for organic luminescence functionlayer, particularly for an electron injection layer, an electrontransport layer, or a hole blocking layer, disposed in contact with acathode or a luminescence layer in an organic luminescence device, theresultant organic luminescence device allows a high-luminanceluminescence at a lower applied voltage and is also excellent indurability.

[0119] The organic luminescence device of the present invention can bereadily prepared by vacuum deposition or wet coating, thus beingproduced in a large-area device relatively inexpensively.

What is claimed is:
 1. An organic luminescence device, comprising: apair of an anode and a cathode, and at least one organic layer disposedbetween the anode and the cathode, wherein said at least one organiclayer comprises a layer of a fused polynuclear compound represented bythe following formula (I):

wherein R₁ to R₁₂ independently denote a hydrogen atom, an alkyl group,a substituted or unsubstituted aralkyl group, a substituted orunsubstituted aryl group, a substituted or unsubstituted heterocyclicgroup, a substituted amino group, a cyano group or a halogen atom; R₁ toR₄, R₅ to R₈ and R₉ to R₁₂ being independently capable of includingadjacent two groups forming a substituted or unsubstituted aliphaticcyclic structure, a substituted or unsubstituted aromatic ringstructure, or a substituted or unsubstituted heterocyclic structure, andX₁, X₂ and X₃ independently denote an oxygen atom, a sulfur atom,C(CN)₂, C(CF₃)₂, C(Ar₁)Ar₂ or N—Ar₃, wherein Ar₁, Ar₂ and Ar₃independently denote a substituted or unsubstituted aryl group or asubstituted or unsubstituted heterocyclic group; Ar₁ and Ar₂ beingcapable of forming a ring structure.
 2. A device according to claim 2,wherein at least one of X₁, X₂ and X₃ in the formula (I) is C(CN)₂.
 3. Adevice according to claim 1, wherein said fused polynuclear compound ofthe formula (I) is represented by the following formula (II):


4. A device according to claim 1, wherein said fused polynuclearcompound of the formula (I) is represented by the following formula(III):


5. A device according to claim 1, wherein said at least one organiclayer comprises a layer comprising at least one species of said fusedpolynuclear compound of the formula (I) disposed in contact with thecathode.
 6. A device according to claim 3, wherein said at least oneorganic layer comprises a layer comprising at least one species of saidfused polynuclear compound of the formula (II) disposed in contact withthe cathode.
 7. A device according to claim 4, wherein said at least oneorganic layer comprises a layer comprising at least one species of saidfused polynuclear compound of the formula (III) disposed in contact withthe cathode.
 8. A device according to claim 1, wherein said at least oneorganic layer comprises a lulminescence layer and a layer comprising atleast one species of said fused polynuclear compound of the formula (I)disposed in contact with the luminescence layer.
 9. A device accordingto claim 3, wherein said at least one organic layer comprises aluminescence layer and a layer comprising at least one species of saidfused polynuclear compound of the formula (II) disposed in contact withthe luminescence layer.
 10. A device according to claim 4, wherein saidat least one organic layer comprises a luminescence layer and a layercomprising at least one species of said fused polynuclear compound ofthe formula (III) disposed in contact with the luminescence layer